Multiband superheterodyne radio receiver having a push-button station selector



H. vM. BACH Il ULTIBAND SUPERI'iETERODYNE RADIO RECEIVER HAVING A PUSHBUTTON STATION SELECTOR Filed Oct. 22', 1945 2 Sheets-Sheet' 1 aiuta@ 1u.: k

R 3mm l -Hmur M. BACH BACH ODYNE H. M. D SUPERHETER RADIO RECEIVER APUSH BUTTON STATION SELEC TOR 2 Sheets-Sheet 2 n LL 3mm/m HENRY M. BACH@M4/ww( M @www cmTI MT 1 LE@ mm @am/ El Ew@ ETRE/ 1 1| NWN@ ma/Mrllllllll 1|. Hum@ @F E- H@ @HQ 1111 Q/, 1%-. Ew@ EU/ D n 1|-1MWU ELE/h/@w M n n A Q/ 2 i 3%: Q v A WQWTJ @www QX me 1|| Patented Nov. 7, 1950MULTIBAND SUPERHETERODYNE RADIO RECEIVER HAVING A PUSIILBUTTON` STATIONSELECTR Henry M. Bach, Woodmere, N. Y.,assignor tarifemier CrystalLaboratories, Incorporated, New

York, N. Y.

Application Gctober 22, 1945, SeriallNo. 623,680

(Cl. Z50-20) 2 Claims.

This invention relates to radio receiving equipment, and moreparticularly to radio receiving equipment of the superheterodyne type.

A main object of the invention is to provide a novel'and improved methodand means of radio reception wherein tuning is accomplished by verysimple manual operations and wherein extreme tuning accuracy,stability,` and reliability of performance is obtained.

A further object of the invention is to provide an improved method ofradio receiver operation wherein tuning is accomplished of any desiredsignal frequency in a given band of frequencies, such as the broadcastband or a short wave band, by the manipulation of a pair of selectedpush button elements A still further object of the invention is toprovide an improved radio receiving structure employing a plurality ofcrystal-controlled component oscillators, the performance of saidstructure being such thattuning `maybe accomplished over a desired ban-dof signal `frequencies.

A Other objects and `advantages of the invention will become apparentfrom :the following dee scription andlclaimsgand from the accompanyingdrawings, wherein l made whereby the ,condensers are tracked at threepoints over the tuningband.

Even if the condensers are initially adjusted 'for satisfactorytracking, they may be subsequently aected by conditions of temperature,`vibration and the like, so as to become misaligned and to therebyreduce the overall sensitivity of the, re ceiver either at certainpoints in the tuning band or entirely over said band. This condition maybe aggravated by further mechanical Inisalign-u ment where push buttonsor other mechanical devices are employed to establish the correct seteting of the ganged tuning condensers, or,`where no tuned input stage isemployed, merely by the thermal warping or axial shifting of the platesof the oscillator condenser.

It is a common fact, therefore, that after a pee riod of use, asuperheterodyne receiver, manually operated bymeans either-of theganged`condenser type or `of the type employing push buttons, will loselsensitivity and selectivity, and in a `majority of cases the`deterioration in performancecan be traced to the` misalignment of theoscillator con.-

denser. f

It i-s `a prime purpose `of this invention to prol vide a system-oftuning for a superheterodyne re Figure 1 isa schematic block diagramillustrativeof a radio receiving system constructed in accordance `withand employing the method of this invention. i t

Figure 2 is aschematic Wiringdiagram` of a lowpass-high pass ilterAemployed in 'the fradio i receiving system ofFigureil.

condenser must be `carefully adjusted to track with the main tuningcondenser to .produce a substantially constant intermediate frequencyvalue forlall signals over the tuning band. `Per-- feet tracking ispractically impossible to obtain,

so that ordinarily, compromiseadjustments are` ceiver wherein novariable oscillator condenser is `employedin tuning the receiver `andwherein the initial conditionsfor producing the correct Value ofintermediate frequency at the input side of the intermediate frequencyamplier are permanently maintained for all channels of a tuningband. j

In the broadcast band extending from 500 kc. to 1590 kc.,l alltransmitting stations operate on multiples of 10 kc., such as 630 kc.,'710 kc., 1500 kc., etc. In tuning the receiver over this band, it istherefore only necessary to tune to multiples of 10 kc. to receive anystation in the band. In the range from 500 to 1590 kc. there arechannels respectively separated by 10 kc. Therefore in order to tune thereceiver to any station in this band it must be possible to set theoscillator or its equivalent to obtain a suitable value of frequencywhich will be variable at least in l0 kc. steps and which will combinewith any signal frequency in the` band to produce the intermediatefrequency, ofthe receiver. y

It is also desirable to eliminate the possibilities of mistuning such asare inherent in the conventional condenser-tunedreceiver employingeither manual tuning or push-button,mechanicalY tunling by kc.

ing, such mistuning usually causing serious distortion. This problem hasheretofore been dealt with by employing a crystal-controlled oscillatorto beat with the signal frequency to produce the desired intermediatefrequency value. As can be readily seen, however, 110 crystals would berequired to operate the oscillator at all of the required frequenciesfor receiving all transmitting stations over the broadcast band, andappropriate switching means would have to be furnished for selectivelyconnecting the crystals into the oscillator circuit. This would resultin a very cumbersome arrangement.

In accordance with this invention, the number of crystals necessary totune to all stations over a desired band is materially reduced byemploying a plurality of crystal controlled oscillators in decadearrangement in place of the single os- Cillator heretofore employed.

Figure 1 shows in outline form the application of the tuning system ofthis invention to a receiver employing two heterodyne stages. In thesystem of Figure 1 the signal input is heterodyned in the firstconverter stage 40| with a yrelatively high frequency crystal-controlledvoltage produced by the first oscillator 402, resulting in a firstintermediate frequency in the neighborhood of 4.3 megacycles. The firstintermediate frequency amplifier 403 is arranged to have very lowattenuation over a well defined band of frequencies ranging, say, from4.26 to 4.35 megacycles, thus acting as a band pass filter for this bandof frequencies. The first oscillator 402 is selectively controlled by avariable crystal arrangement 404 comprising a bank of eleven crystalsdiffering in frequency by 100 kc. For tuning the system to the broadcastband of frequencies from 500 to 1590 kc. these crystals range from 4850kc. to 5850 kc. For the band of frequencies from 500 to 590 kc., the rstoscillator 402 is connected to the 4850 kc. crystal. `A 500 kc. signalwill beat with 4850 kc. to produce a 4.35 megacycle first intermediatefrequency, whereas a 590 kc. signal will beat with 4850 kc. to produce a4.26 megacycle first intermediate frequency. Therefore any signalbetween 500 kc. and 590 kc. will produce an intermediate frequency whichwill be passed by the first intermediate frequency amplifier 403 whenthe 4850 kc. crystal is connected to the first oscillator. The followingtable indicates the respective 100 kc. bands tuned by the firstoscillator crystals:

The second oscillator 405 must provide a frequency which will beat withthe first intermediate frequency to accurately produce in the secondconverter stage 401 a second intermediate frequency of 175 kc. Since thefirst intermediate frequency may have any 10 kc. value between 4260 kc.and 4350 kc., the second oscillator crystal bank, indicated as Variablecrystal arrangement 406, must comprise a series of ten crystals differ-This series may begin at 4085 3Q,

Second Osc. Crystal Frequency 4085 kr' 4095 lff 4105 kc 4115 kc 4125 kf'4135 1U 4145 kc 4155 kf 4165 kr' 4175 kr To tune to a 630 kc. signal,for example, the first oscillator 402 is connected to the 4950 kc.crystal. The first oscillator frequency beats with the 630 kc. signal toproduce a first intermediate frequency of 4320 kc. The 4145 kc. crystalis connected to the second oscillator 405 in accordance with the abovetable wherein the 4145 kc. crystal appears opposite 30, representing thelast two digits of the desired channel. The 4145 kc. second oscillatorfrequency beats with the first intermediate frequency of 4320 to producethe desired 175 kc. second intermediate frequency voltage which carriesthe signal modulations.

The above described system of Figure l may also be employed to tune toany one of the 110 channels l0 kc. apart extending from 9110 kc. to10,200 kc. Thus, a 9110 kc. signal will beat with the 4850 kc. crystalfrequency of the first oscillator 402 to produce an intermediatefrequency of 4260 kc., and a 9200 kc. signal will beat with the 4850 kc.frequency to produce an intermediate frequency of 4350 kc. Similarly, a10,110 kc. signal will beat with the 5850 kc. crystal frequency toproduce the 4260 kc. intermediate frequency and a 10,200 kc. signal willbeat with said 5850 kc. crystal frequency to produce the 4350 kc.intermediate frequency.

By an appropriate adjustable low-pass-highpass filter 408 ahead of thefirst converter 40| the system may be set'for either broadcast or shortwave reception. As shown in Figure 2, filter 408 comprises reactors L4and C4 and a switching arrangement including a pair of switch arms |32and |33 mechanically linked together. The connections are so arrangedthat in one position of switch arms |32 andV |33, for example, theposition shown in Figure 2, the filter functions as a low-pass filter topass broadcast frequencies and to exclude higher frequencies, whereas inthe other position of said switch arms, shown in dotted view in Figure2, the filter functions as a high-pass filter, passing the higherfrequencies and excluding the broadcast frequencies.

Referring to Figure 3, a detailed arrangement is shown for tuning thesystem of Figure 1. Mounted on a panel board |30 are two rows ofconventional single-pole single-throw push `button switches, there beingeleven push button switches, numbered from 205 to 2|5 respectively inthe left row and ten push button switches, numbered respectively from300 to 390 in the right row.

The eleven push button switches 205 to 2|5 respectively control thecircuits for a first bank 404 of eleven crystals indicated as X5, Xs,X7, Xs, X9, X1o, X11, X12, X13, X14, and X15, differing respectively infrequency by kc. as above described, and adapted to be selectivelyconnected by aCuatOIl 0f the push button switches 205 to 2 '55551171181frequency' controlling element of first oscillatorl 402i i The ten` pushbuttonswitches 30`0to 390respectively control the circuits forasecond-bank 400' offucrystals, indicatedI as-Vho; Vio, Vio, V30, VineV50; V'tn', Vio, Vac, and" Vu; diifferi'ng-` respectively inL frequencyby 101 kc. as"` above described',` and adapted tobeiselectivelyconnected by actuation ofthe pushr buttonl switches 300 to 390i as thefrequency controlling element ci secondi oscillatorl 405'.-

The first bank oftcrystals 1X5 to XieA corresponds to variable crystalarrangement 404`-and`1 the second bank of crystals Vootol Viaucorresponds to variable crystal arrangement 406i ofi' Figurell.

Aconventionalmechanical'arrangement i's providedwhereb'y any pushbuttoninfeach row may be actuatedl t`oclose l its `corresponding switchcontacts, allV other push buttons of each row being released to maintaintheir switch contacts open. This enables any one' of the crystals X5 toX15 to be connected. to oscillator 402 and anyone of the crystals Von toVac to be connected to-` oscillator 405 at a given time.

Oscillators 402 and 405 may -be conventional oscillators similar to thePierce type. c

CrystalsXs to-Xis are separ-atediin frequency by 100 kc.and-crystalsVonA tolls()` are separated in frequency* by kc.` Y Thefrequency offoscillator 402 can therefore-be'varied in 100 kc'. stepsand thefrequency-ofV oscillator 405- can be varied in 10 kc; steps. A i

Provided on panelA |30 -atone side; for example, at'theleftofeach-ofpush-button switches 205 to 2 I5, is a translucent window IBcarrying a number, the numbers being from 5 consecutively to I5,

corresponding to 100 kc. intervals vfrom 5,00'kc. to 1500 lic. Abovethisrovv of windows the panel may carry identifying indicia such as BCto indicate that this row of windows is for the broadcast band.Similarly, translucent windows I'I are provided at the left of pushbutton switches 300 to 390, each window carrying a number, the numbersbeing 00 to 90 corresponding to 10y kc. intervals.

At the right of push button switches 205 to 2 I 5 are translucentwindows I8 carrying numbers from 0I consecutively to I0 I, correspondingto 100 kc. intervals from 9100 kc. to 10,100 kc., and at the right ofpush button switches 300 to 390 are translucent windows I0 carryingnumbers |00 to I0, corresponding to 10 kc. intervals in the respective100 kc. steps. The right h-and windows may carry identifying indiciacaptions such as SW to indicate that these windows are for the shortwave band. It will be noted that the numbering of the SW windows forpush button switches 300 to 300 is reversed in sequence with respect tothe numbering for the BC windows. By consulting the crystal frequencytables given below it will be seen that this is necessary in order toproperly select the frequency indicated by the additive combination ofthe numbers associated with the rst row of push buttons and the secondrow of push buttons.

Suitable lamps 20 and 2l controlled by a switch arm |34 mechanicallycoupled to the actuating mechanism for switch arms |32 and I 33 ofadjustable lter 408 may be provided behind the respective translucentwindows to illuminate respectively the BC windows when lter 408 is setfor broadcast reception and the SW windows when the filter is set forshort wave reception.

In the specic form of the invention herein describedV the crystals iillustrated? in Figure` El.` have frequenciesgiven by the followingtable:

While-certain'numerical values have been mentioned in-`connectionwiththe method and elements-ofthe specic embodiment oftheinvention describedi above, these values arefmerely illustr-ative'ofapractical example of the invention and are not to beconstrued` aslimiting. Other intermediateifrequencyvalues may be employed` thanrthose specied' above, i and' of courseV the` crystal frequenciesemployed in the decade` oscillators would be changed in accordance withthe different intermediate frequency values employed. The new crystalfrequencies could be readily calculated by one skilled in the art.

While a, certain specic embodiment of a method and means for receivertuning has been disclosed in the foregoing description, it lwill beunderstood that numerous modifications within the spirit of theinvention may occur to those skilled in the art. Therefore it isintended that no limitations be placed on the invention other than asdened by the scope of the appended claims.

What is claimed is:

l. Means for tuning a radio receiver comprising an inductance, acapacitance, a double-pole double-throw switch, the rst pole of saidswitch having first and second contacts associated therewith and thesecond pole of the switch having third and fourth contacts associatedtherewit the switch being arranged so that in a rst position thereof thepoles respectively engage the iirst and third contacts and in a secondposition thereof the poles respectively engage the second and fourthcontacts, the inductance having one terminal thereof connected to saidfirst and fourth contacts, the capacitance having one terminal thereofconnected to the second and third contacts, the remaining terminals ofthe inductance and capacitance being connected together and defining anoutput terminal, whereby in the rst position of said switch theinductance is connected between said iirst pole and said outputterminal, providing a low-pass arrangement and in the second position ofsaid switch the capacitance is connected between said rst pole and saidoutput terminal, providing a high pass 7 arrangement, so that in thefirst position the arrangement excludes frequencies above apredetermined value and in the second position the arrangement excludesfrequencies below said predetermined value, a rst variably tunedoscillator, means for combining the output of said first oscillator withradio frequency energy at the said output terminal, a second variablytuned oscillator, and means `for ycombining the output of said secondoscillator with. the resultant frequency derived from combining theoutput of said rst oscillator and the energy'at said output terminal.

2. Means for tuning a radio receiver comprising an inductance, acapacitance, a double-pole double-throw switch, the first pole of saidswitch having rst and second contacts associated therewith and thesecond pole of said switch having third and fourth contacts -associatedtherewith, the switch being arranged so that in a rst position thereofthe poles respectively engage the first and third contacts and in asecond position thereof the poles respectively engage the second andfourth contacts, the inductance having one terminal thereof connected tosaid first and fourth contacts, the capacitance having one terminalthereof connected to the second and third contacts, the remainingterminals of the inductance and capacitance being connected together anddefining an output terminal, whereby in the first position of saidswitch the inductance is connected between said first pole and saidoutput terminal, providing a low-pass arrangement and in the secondposition of said switch the capacitance is connected between said firstpole and said output terminal, providing a high-pass arrangement, sothat in the first position the arrangement excludes frequencies above apredeterrst crystals to said rst oscillator, means for,-

combining the output of said first oscillator with radio frequencyenergy at the said output terminal, a second oscillator adapted forcrystal control, a second bank of crystals separated in frequencyY -by aconstant relatively small value,

means for selectively connecting any one of saidV second `crystals tosaid second oscillator, and means for combining the output of saidsecond oscillator with the resultant frequency derived from combiningthe output of the rst oscillatorVV and the energy at said outputterminal. HENRY M. BACH.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 2,061,740 Rechnitzer Nov. 2.4,1936 2,074,800 Mountjoy Mar. 23, 1937 2,145,676 Zepler Jan..31, 19392,151,810 Siemens Mar. 28, 1939 2,245,385 Carlson June 10g-19412,323,924 Mayer July 13, 1943 2,354,148 Shaw July 18, 1944 2,383,322Koch Aug. 21, 1945 FOREIGN PATENTS Number Country Date 339,316 GreatBritain Dec. 5, 1930

